Cold head stamped fastener inserts including selectively removable tangs

ABSTRACT

The present invention provides for fastener inserts and methods of manufacturing the same. The fastener inserts include selectively removable tangs which can be broken away more cleanly than with other commercially available fastener inserts. Further, the methods of manufacture offer a significant improvement in the production process.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional application of U.S. patentapplication Ser. No. 09/815,799 filed on Mar. 23, 2001. The disclosureof the above application is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to fastener inserts and, moreparticularly, to fastener inserts including a cold head stamped detentto form selectively removable tangs, an apparatus for cold head stampingfastener inserts and methods of manufacturing cold head stamped fastenerinserts.

BACKGROUND OF THE INVENTION

[0003] Fastener inserts of varying design for maintaining a fastenerwithin a tapped hole or nut assembly are commonly employed. The use ofsuch fastener inserts offer many advantages including, by way ofnon-limiting example, providing a more balanced distribution of dynamicand static loads throughout the length of engagement between fastenersand the substrate.

[0004] To facilitate the disposition of the fastener insert within atapped hole or nut, often such inserts are provided with a selectivelyremovable tang. The tang typically includes a notch which is milled,sheared, cut or ground into the insert which allows the tang to bebroken off. Once the fastener insert is properly positioned within thetapped hole or nut, pressure is exerted on the tang which causes thetang to break away from the fastener insert body and provide anunencumbered passageway for the insertion of a fastener.

[0005] The notch on the removable tang has heretofore been formed viamilling, shearing, cutting or grinding using a notch cutter or similartool prior to coiling the wire. In order to carry out the notching step,the wire must be stopped in the middle of the cycle and prior to thecoiling step which adds to the time and expense of manufacturing. Whilethe invention of EP 1060812 A2 attempts to address certain problemsassociated with stopping or significantly slowing down the productionprocess, this document appears to relate to fastener inserts formed frompre-spooled or pre-rolled wires including milled or sheared notches. Asa result of notching and rolling the wire and subsequently coiling thewire, a variation on the insert outside diameter and length can resultwhen utilizing different lots or reels of stainless steel wire. Thus,pre-forming the notch on a whole reel of the material could result inprocessing problems during the coiling operation. This is based on thefact that if the insert diameter or insert length changes due tovariation in the wire spring back, the pre-determined location of thenotch will not meet location requirements for proper tang break-offafter installation. The helically coiled insert will not be dimensionedcorrectly. The whole reel of pre-notched wire will have to be scrapped.

[0006] Another critical element that can result in material damage orlosses is based on the fact that the majority of the wire utilized tomanufacture the helically coiled inserts are of small diameter in theareas of 0.010″ to 0.050″. Based on this fact, a pre-notched reel ofwire contains thousand and thousands of strands and tens of thousands ofnotches. It would be very easy for this wire to be tangled, nicked or tobreak at any of the pre-notched locations if not handled with extremecaution and care. This can further result in additional material lossesor operating and set up problems during the coiling operation.

[0007] Further, there are certain safety issues introduced into themanufacturing process as a result of milling, such as metal chipformation. Sharpening of the milling apparatus also may pose certainrisks.

[0008] Yet another problem with heretofore known fastener inserts is theinability to identify similarly shaped inserts from one manufacturer tothe next. This is especially problematic where fastener insert qualityvaries among manufacturers.

[0009] In view of the foregoing, a notched fastener insert which solvesone or more of the enumerated problems is desirable.

SUMMARY OF THE INVENTION

[0010] The present invention therefore relates to a method ofmanufacturing an insert comprising the steps of:

[0011] a) providing a wire;

[0012] b) cold head stamping the wire to form a detent in said wire;

[0013] c) coiling the wire to form a helically coiled body; and

[0014] d) bending an end of said wire in proximity to said detent toprovide a selectively removable tang.

[0015] The present invention further relates to a fastener insertcomprising:

[0016] a wire body having a plurality of convolutions;

[0017] at least one detent cold formed into said wire body; and

[0018] a selectively removable tang extending from said body inproximity to said at least one detent.

[0019] Still another aspect of the present invention is a method ofmarking fastener inserts, wherein the me the method generally comprisesthe steps of:

[0020] a) providing a wire;

[0021] b) cold head stamping marking on said wire; and

[0022] c) coiling the wire to form a helically coiled body.

[0023] The present invention further relates to a fastener insertcomprising:

[0024] a wire body having a plurality of convolutions; and

[0025] a marking stamped into said wire body to provide an identifier onsaid insert.

[0026] An apparatus for cold head stamping wire to be formed intofastener inserts is also provided in accordance with the teachings ofthe present invention. The cold head stamping apparatus for use inassociation with wire comprises:

[0027] a fixture;

[0028] a selectively extendable and retractable stamping die supportedby said fixture for stamping a detent into said wire; and

[0029] an actuator for intermittently extending and retracting saidstamping die.

[0030] In contrast to milling, the cold head stamping of a detent inaccordance with the teachings of the present invention, eliminate theissues of metal chip formation and ejection and repeated toolsharpening. Further, the cold head stamping process can be carried outbefore or during the coiling step which is preferred and gives rise toshorter production cycle times. Additionally, as a result of the coldhead stamping, the notch itself is improved to give a cleaner, moreefficient break point between the tang and the body of the fastenerinsert.

[0031] The ability to mark the fastener inserts with an identifierdesignating the manufacturer, material or other pertinent informationcan have a significant impact on quality control considerations.

[0032] Further areas of applicability of the present invention willbecome apparent from the detailed description provided hereinafter. Itshould be understood that the detailed description and specificexamples, while indicating the preferred embodiment of the invention,are intended for purposes of illustration only and are not intended tolimited the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

[0034]FIG. 1 is a schematic view demonstrating the steps ofmanufacturing a cold head stamped fastener insert;

[0035]FIG. 2 is a perspective view of a first cold head stampingapparatus useful in forming cold head stamped fastener inserts;

[0036]FIG. 2A is a perspective view of the detent formed via theapparatus of FIG. 2;

[0037]FIG. 3 is a front view of the extendable and retractable stampingdie of the cold head stamping apparatus of FIGS. 1 and 4;

[0038]FIG. 4 is a magnified perspective view showing the retractablepunch of a cold head notching apparatus engaging the wire of thefastener insert;

[0039]FIG. 5 is a cross-sectional view of the cold head stamping fixtureand stamping head;

[0040]FIG. 6 is a perspective view of a second cold head stampingapparatus useful in forming cold head stamped fastener inserts;

[0041]FIG. 6A is a perspective view of the detent formed via theapparatus of FIGS. 5 and 6;

[0042]FIG. 7 is a perspective view of a fastener insert manufacturingprocess wherein the cold head detent and cold head marking functions areperformed at separate stations along the process;

[0043]FIG. 7A is a perspective view of the detent and marking formed viathe apparatuses of FIG. 7; and

[0044]FIG. 8 is a front view of the extendable and retractable stampingdie of the cold head marking apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] The following description of the preferred embodiment(s) ismerely exemplary in nature and is in no way intended to limit theinvention, its application, or uses.

[0046] Referring to FIGS. 1 and 2, the process of cold head notching afastener insert to provide a readily removable tang is demonstrated. Awire formed from a desired alloy such as stainless steel, by way ofnon-limiting example, is provided. The wire which is generally preformedto the desired circumferential geometry through a die head 10 isadvanced throughout the fastener insert production process by a knownautomated feeding apparatus (not shown).

[0047] The wire is further advanced to a cold head stamping station 12wherein at least one detent of predetermined shape and depth is providedin the wire. Under a preferred embodiment, as will be described ingreater detail below, the wire is optionally provided with a marking atthe cold head stamping station or at a separate cold head stampingstation which can serve as a product and/or source identifier for theresulting fastener insert.

[0048] The detent can have a variety of shapes conducive to the removalof the resulting tang, but it is preferred that the detent have asubstantial V-shape when viewed from the side with converging angledfaces of between about 60° and 120°. In general, in order to obtain aneffective cold head stamped detent for purposes of generating aselectively removable tang, the detent should have a minimum depth ofabout 30% of the wire thickness or width (single sided).

[0049] After stamping the wire 14 to provide at least one detent andoptionally marking the wire, the wire is advanced and coiled to form thefastener insert body.

[0050] Thereafter, the leading end 16 of the coiled fastener insert bodyis bent in relative proximity to and before the at least one detent toprovide a selectively removable tang 18.

[0051] Referring to FIG. 2, there is shown a cold head stamping station12 including a first cold head wire stamping apparatus 20 used to carryout the detent formation step discussed above. The apparatus 20generally includes a fixture 22, a selectively extendable andretractable stamping die 24, and an actuator 26. The actuator 24 may bemanually operated or may be computer linked to the PLC controller 28.The fixture 22 as shown in FIG. 5 includes an enclave 30 which housesthe trailing end 32 of the stamping die. The fixture also includes aplunger 34 for activating the extension and retraction of the stampingdie 24 upon receiving a signal by the activator.

[0052] The stamping die 24 includes a body 36, the trailing end of whichis housed within the fixture 22. The stamping die also includes a head38 for forming a detent into the wire 14. The head 38 generally includesfirst and second angularly advancing walls 40 and 42 as best shown inFIG. 3 which converge at a point 44 which is sufficiently sharp topenetrate and displace enough of the wire to form a detent 50.

[0053] As shown most clearly with reference to FIG. 3, angular wall 40of the stamping die 24 generally includes a projection or recess 46which is shaped such as to leave a marking along a surface of the detentas illustrated in FIG. 2A. As noted above, the marking can be useful asa source or product specification identifier. This marking 52 shouldgenerally occur along surface 54 of the detent as this portion remains apart of the fastener insert after the selectively removable tang 18 isbroken away.

[0054] It is preferred that the cold head stamping apparatus 20 of FIG.2 include a grooved backing plate 60. The backing plate 60 should have asufficient strength to appropriately support the wire 14 as it is beingstamped. The groove 62 is shaped such as to mate with the geometry ofthe wire to prevent undesired displacement of the wire during thestamping operation.

[0055] Referring to FIG. 6, a second cold head stamping station 12Aincluding mutually opposing cold head stamping apparatuses 20 and 20Aare provided. The stamping apparatuses 20 and 20A, generally include allof the same components as the stamping apparatus depicted in FIG. 2.

[0056] Preferably, the apparatuses 20 and 20A and, more particularly,the selectively extendable and retractable stamping dies 24 and 24A arecycled to simultaneously contact the wire from opposing directions so asto not displace the wire during the detent forming operation. As aresult, a pair of mutually opposing detents 50 and 50A are providedalong opposite sides of the wire as shown in FIG. 6A. According to thisembodiment, the depth of each of the detents 50 and 50A should be on theorder of at least about 15% of the wire thickness or width (dual sided).Again, one or both of the stamping dies can be provided with projectionsor recesses to mark the wire along at least one of the resultingdetents.

[0057] Referring to FIG. 7, a perspective view demonstrating analternative process is shown. According to this process, the wire 14 ismarked along a length of the wire other than the detent 50. Thus, afirst cold head stamping station 12 is provided for purposes of formingthe detent 50 and a second cold head stamping station 66 is provided forpurposes of generating a marking on the wire. The cold head stampingstation 12, while shown as the single detent forming variety asillustrated in FIGS. 2 and 2A, could also be in the form of a dualdetent forming station as shown in FIGS. 6 and 6A.

[0058] The cold head marking apparatus 66 also generally includes afixture 68, a selectively extendable and retractable stamping die 70, anactuator 72 and a computer 74. The stamping die 70 includes a wall 76having a projection or recess 78 for leaving a marking along the wire asshown in FIG. 8.

[0059] In view of the above described apparatuses, the production of ahelically coiled fastener insert will now be described in greaterdetail. Once the cold heading fixture has been set up and positioned,wire is fed through the die head 10, cold head fixture 22 and then ontothe selectively retractable mandrel 80. The wire is advanced and thewire is wound over the mandrel 80 which is rotated in a first direction.When the wire is advanced to the point that the coil is formed to thedesired length, the mandrel 80 direction in reversed and the mandrel isgenerally retracted. At the end of the reverse cycle, the completedinsert is cut off from the rest of the wire by cutter 82. It is at thispoint, while the cutting operation is occurring and the wire ismomentarily stopped, that the stamping operation to form one or moredetents, and preferably one or more markings occur. Generally, the coldheading stamping and marking takes place about one to three wire insertlengths away from the part that is being coiled. While the distance canbe shorter or greater, depending on insert size and length, thisdistance allows for calibration of the equipment without requiring atotal shut down.

[0060] Cold heading the insert detent in this fashion internally to thecoiling process is preferred over other suggested methods where thenotch is formed in separate and distinct operations either before orafter the coiling process. This process offers many distinct advantagesover other processes. It provides flexibility to perform setupadjustments and make numerous corrections to the various insert featuressuch as insert length adjustment, tang length and insert outer diameteradjustments, by way of non-limiting example, without affecting therequired location of the detent on the insert.

[0061] Not only do the above described apparatuses speed up theproduction process by eliminating the need to stop the advancement ofthe wire while forming the detent, but the detent forming step itself ismuch faster than with cutting, milling or shearing. Additionally, theresulting fastener inserts tend to be improved. For example, it has beendetermined that the portion of the wire along and below the detent hasan increased hardness of approximately twenty percent, e.g., a stainlesssteel wire having a hardness of between about 29 RC to 30 RC exhibits ahardness of at least about 36 RC along and below the detent. Thisincreased hardness along and below the detent makes the material morebrittle and forms a stress point which in turn allows the selectivelyremovable tang to be broken off cleaner and with less force as comparedto other known fastener inserts.

[0062] In order to demonstrate one or more of the advantages describedherein, helically coiled fastener inserts having cold head stampeddetents were manufactured from stainless steel wire, such that thedetents had a depth of forty percent of material depth. The inserts werethen mounted onto a fixture and linear pressure was applied to theremovable tang in order to break off the tang. It was observed thatapproximately 38-40 ft. lbs. of force was required to break off thetangs cleanly from the rest of the insert.

[0063] Helically coiled fastener inserts formed from the same stainlesssteel wire, were notched using conventional milling techniques. Thenotch on these inserts were also developed to a depth of forty percentof the material depth. These inserts were also mounted to the samefixture and were processed through the same tests. After reachingreadings of 40-45 ft. lbs., the tangs of the inserts would not breakoff. Once more force was applied, the result was to cause the insert topull out of the holding fixture without breaking off the tang. The depthof the notch had to be increased to 50% of the material depth before thetangs broke off at the 40 ft. lbs. level.

[0064] Thus, not only does the present invention offer significantreduction in production times necessary to manufacture an insert, butalso gives rise to an improved fastener insert.

[0065] The description of the invention is merely exemplary in natureand, thus, variations that do not depart from the gist of the inventionare intended to be within the scope of the invention. Such variationsare not to be regarded as a departure from the spirit and scope of theinvention. For example, the detent or detents can be found in the faceof the wire (width) as illustrated or it can be formed tangent to theheight of the wire.

What is claimed is:
 1. A fastener insert comprising: a wire body havinga plurality of convolutions; at least one detent cold formed into saidwire body; and a selectively removable tang extending from said body inproximity to said at least one detent.
 2. The fastener insert of claim 1wherein said at least one detent has a V-shape.
 3. The fastener insertof claim 2 wherein said at least one detent has a minimum depth of about30%.
 4. The fastener insert of claim 1 wherein said at least one detentincludes a pair of mutually opposing detents occurring along oppositesides of said wire.
 5. The fastener insert of claim 4 wherein eachdetent of said pair of mutually opposing detents has a minimum depth ofabout 15%.
 6. The fastener insert of claim 1 wherein said wire has anincreased hardness along said detent.
 7. The fastener insert of claim 1further comprising a marking provided along said wire.
 8. The fastenerinsert of claim 7 wherein said marking is provided along said detent. 9.A fastener insert comprising: a wire body having a plurality ofconvolutions; and a marking cold head stamped into said wire body toprovide an identifier on said insert.
 10. The fastener insert of claim9, wherein said wire includes at least one detent with which saidmarking occurs.
 11. The fastener insert of claim 10, wherein said atleast one detent has a V-shape.
 12. The fastener insert of claim 11wherein said at least one detent has a minimum depth of about 30%. 13.The fastener insert of claim 10 wherein said at least one detentincludes a pair of mutually opposing detents occurring along oppositesides of said wire.
 14. The fastener insert of claim 13 wherein eachdetent of said pair of mutually opposing detents has a minimum depth ofabout 15%.
 15. The fastener insert of claim 10 wherein said wire has anincreased hardness along said detent.